The Boschman automold machine is utilized to encapsulate electronic components such as integrated circuits in a plastic material. Circuit dies are fabricated or die cut from wafer material and then added to a substrate material forming a circuit sub-assembly. The circuit sub-assemblies are run through the Boschman machine to encapsulate the parts in plastic to protect the circuits dies and leads or wire bonds from damage.
The Boschman machine operates in a manner where the circuit sub-assemblies are automatically fed into the mold section of the machine with one sub-assembly disposed in each mold cavity. Plastic material is then injected through a sprue into the mold cavities to encapsulate the subassemblies. The encapsulated components are then automatically ejected or unloaded from the machine. The plastic material is initially provided in the form of a pill or pellet and may consist of any number of materials such as a thermoset resin or a melamine compound or the like. The pellets are automatically transported by a pellet boat which individually delivers a pellet to a pot adjacent each mold cavity. The mold section is heated to liquefy the pellets prior to injection of the plastic material into the mold cavities.
The mold cavities and material transport passages of the automold machine must be cleaned periodically to remove excess material and contaminants. The automold machine runs on a continuous cycle or process.
One method of cleaning requires the machine to be shut down long enough for a technician to remove the mold from the machine, replace the mold with a spare, and restart the machine. This process requires significant down time for the machine, which is on the order of 60 minutes for each cleaning cycle. This method requires having a spare mold, which is an added expense. Further, the removed mold must also be cleaned, adding time to the cleaning cycle.
An additional method of cleaning may be performed by running cleaning pellets directly through the machine through the production process path. One problem with this method is that the cleaning pellets are often of a different size than the plastic material pellets. To run a continuous line, the system can only handle one size pellet and therefore the machine must be shut down to convert the system to accept the odd size cleaning pellets. Another problem with this method is that the machine must be completely evacuated of process pellets before loading the cleaning tablets or pellets into the automatic feed system to avoid mixing of materials. The cleaning pellets leave a residue throughout the process path and handling system if run through the machine in this manner. One or more cleaning pellets may even be left in the system when converted over to the process pellets. This causes cleaning material to mix with the plastic material contaminating any parts encapsulated with the mixed materials. The procedure necessary to ready the mold for the cleaning process and production processes are different. If the set-up for the production process is not done perfectly after the cleaning process is complete, the mold must be re-conditioned causing further downtime of the automold machine.
An additional problem with the present machine is that it is difficult and time consuming to do a test or experimental run for materials other than the production pellet material. This is because, again, the machine must be shut down and evacuated of all production pellet material prior to performing the test. Once a test is completed, the machine must again be shut down for conversion back to production material. Because the machine must be shut down, it would be very time inefficient and therefore undesireable to attempt to run a low volume test, such as a single shot test.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for an improved apparatus for and method of cleaning a Boschman automold machine which results in a more reliable production mold process, requires less machine downtime, and is easier to perform than conventional known methods.